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MG Midget and Sprite Technical - Mounting the Carbs

What is the best practice when installing the carbs?

I have four flat washers and plain nuts for which to use in remounting my carbs (1098 10CC engine). These are the parts shown in the catalogs, and exactly what was holding the carbs in place when I removed them.

From reading here and elsewhere, when tightening fasteners the theory is that when properly torqued they will not vibrate loose because the studs (or bolts) stretch a bit keeping the assembly under tension. The problem is without a special tool I cannot measure the torque on these nuts, which are fairly inaccessible behind the carbs. Do I just tighten them snugly or should I use a lockwasher or Loctite?

Is there a reason the factory did not use lockwashers in this application? Without them it seems to me that it would be way too easy for the carbs to vibrate loose.

Also I am assuming that I should not use gasket sealer on the paper gaskets between the manifold/heat shield/spacer/carburetor. Is that correct?
Paul Noeth

You just tighten them up with the standard length open ended spanner. The length of standard spanner is designed so that one naturally exerts the correct torque on the nut.

The originals of these engines used a brass full nut on those exhaust studs. The theory was that as the exhaust heats up the brass expands more than the steel of the stud, and expands along the length of the stud, increasing the clamping pressure on the manifold flange.
Guy W

Yep just tighten them normaly and it won't fall off

Onno (you don't need a torque figure for every bolt, comonsense will do just fine) Könemann
Onno K

Well said Onno. I only use a torque wrench for really critical bolts like crank journals, cylinder head and suspension pivots. All the rest just need to be tight, not strangled, just tight.

To answer Paul's secondary question, no, you don't use any sealer on the gaskets between the various inlet tract components.
Mike Howlett

I use these long brass nuts from Minispares or Minimania in your neck of the woods.

You get better strength because they use all the thread, they are easier to get a spanner or socket on and because they cover the thread they stop it corroding.
John Payne

I use white leitium grease on the manifold gaskets...it seals nicely with heat and makes the makes the gasket reusable....i also do the same with the cork gasket on the valve cover

Prop
Prop and the Blackhole Midget

I think paul is mounting the carbs to the manifold. We seem to have strayed to manifold to head nuts.

Just nip them up snugly. They don't normally come loose.

John, do you have a link or a part number for the long brass nuts?
Dave O'Neill2

As Paul mentioned the 4 large flat washers I presumed he was meaning those used at the manifold to head joint. But my original point remains the same. Use the correct sized spanner and the length of it is designed to give the correct torque assuming you use firm pressure and don't over exert yourself!
Guy W

Dave,

Long brass nuts [item 27] are available from the MGOC:

http://www.mgocspares.co.uk/acatalog/MGOC_SPARES_MANIFOLD__midget__176.html#l27


HTH
Doug Plumb

Thanks Doug
Dave O'Neill2

Long brass nuts....hahaha

Just make sure you dont cover the vent hole on the carb face with the gasket or it wont run well

Prop
Prop and the Blackhole Midget

Not only did I go down the wrong route but I forgot to post the link!!

Anyway, Doug has found them at a better price than Minispares:

http://www.minispares.com/product/Classic/Engine/Cylinder_heads/Studs_bolts_nuts/51K1177.aspx?
John Payne

Thanks john

So thats what those are to... Ive got several in a nut jar at the shop, i didnt know where they came from

Prop
Prop and the Blackhole Midget

I over tightened a carb nut once and split the casting. Snug up as indicated above and you should not have any vacuum leaks.

Glenn Mallory

I'm a big fan of the later spec brass nuts with built in washers. That way there's only one thing to retrieve when it drops and bounces under the workbench.

http://www.minispares.com/product/Classic/Exhaust_and_manifold/Inlet/Inlet/LYH10008.aspx?110202
Growler

nearly 5 pounds EACH, cripes are they made of unobtainium??
David Smith

Growler if it's a 10p nut it can bounce under the bench and hide there for eternity, but at £5 if it tried to fall of the stud and roll away I'd make it suffer big time when I put the spanner back on it, although at that price it should tighten itself up.

I assume you get them from a local supplier who isn't as dear?

Greg H

Ever since paying $15 each for single-use head bolts (18 thereof) for one particularly exotic engine, I have suspected my financial pain threshold might be a bit out of whack.

That said, far too many times have I have burnt, grazed, pinched, and cut myself, sheared rusty studs, re-faced bent and deformed washers, dropped them over and over again, and mole-gripped rounded off nuts with deformed threads, all in the pursuit of simply detaching an inlet or exhaust manifold.

Just thinking of how easy these nuts (plus stainless studs) make the job is enough to banish any guilt at spending £30 on them.
Growler

I think Onno hit the nail on the head; (you don't need a torque figure for every bolt, comonsense will do just fine).

Back when I was young (I bought this car in 1972) I didn't have a torque wrench and tightened things using common sense. As I got older and wiser (??) I tried to do more things by the book, relying less and less on good old common sense. I appreciate the reminder.

I do like Prop's suggestion to use white lithium grease on the gaskets. It doesn't seem like there would be any negative consequences to using it and it may make the carbs easier to remove in the future.

Thanks to all for your insights.

Paul
Paul Noeth

This thread was discussed between 19/12/2012 and 26/12/2012

MG Midget and Sprite Technical index

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